Phytopathogenic fungi are the causal agents for many diseases that infect and destroy crops. In particular, the diseases sugar beet cercospora leaf spot, apple scab, tomato early blight, banana black sigatoka, peanut leaf spot, and grape and pepper botrytis are especially devastating.
Sugar beet is susceptible to many foliar diseases caused by phytopathogenic fungi. One of the most frequently encountered and destructive foliar diseases occurring on sugar beet is sugar beet cercospora leaf spot, caused by the fungus, Cercospora beticola. Sugar beet cercospora leaf spot is common to sugar beet plants throughout the world, and is particularly destructive in regions with wet, warm growing seasons, such as Western and Southern Europe, and the Midwestern United States. During periods of high temperature and wetness, sugar beet cercospora leaf spot spreads rapidly in the field. Ultimately, the disease kills sugar beet leaf tissue, resulting in reduced sugar beet weight and sugar content.
The leaves and fruit of apple trees are susceptible to attack by a fungus, Venturia inaequalis, resulting in a disease called apple scab. The disease occurs wherever apples are grown, but is most common in the United States and Europe. Uncontrolled, apple scab results in deformed, low quality fruit.
Tomatoes are also susceptible to diseases caused by fungi. For example, the foliage, stem and fruit of the tomato plant may be attacked by a fungus, Alternaria solani, resulting in a disease called tomato early blight. Tomato early blight occurs wherever tomatoes are grown, but is particularly destructive in regions with wet or humid climates. Uncontrolled, tomato early blight causes the defoliation of the tomato plant, resulting in reduced fruit number and size.
The leaves of the banana plant are also subject to attack by fungi, for example, Mycosphaerella fijiensis, which causes a disease called banana black sigatoka. Uncontrolled, banana black sigatoka kills the leaves of the banana plant, resulting in small, poor quality fruit. Because bananas are a major export for many Latin American and other tropical countries, the control of banana black sigatoka is critical to those countries' economies.
Currently, only five fungicide classes are used to treat banana black sigatoka. In some areas, the offending fungus has become resistant to the two most effective of those fungicide classes. The result has been more intensive spraying with the less effective fungicides. Therefore, there is a need for new fungicides with other modes of action for the continued protection of bananas.
Peanut leaf spot, caused by fungi of the Mycosphaerella genus, such as Mycosphaerella arachidis, but more importantly fungi such as Cercospora arachidicola and Cercosporidium personatum, is the most destructive foliar disease of peanut plants in the southeastern United States. Uncontrolled, peanut leaf spot causes the rapid defoliation of entire fields, resulting in reduced pod size and number. To date, management of peanut leaf spot has been difficult. Because of the development of resistance to certain fungicides, and the repeal of regulatory approval for other fungicides, ninety-nine percent of the peanuts grown in this region are sprayed with a single fungicide.
Grapes and peppers are susceptible to attack by the fungus, Botrytis cinerea, causing grape botryitis and pepper botrytis, respectively. Grape botrytis, for example, is an especially destructive disease that destroys the cell walls of the fruit, resulting in bunch rot. Grape botrytis occurs wherever grapes are grown, but is most common in Europe.
In spite of the commercial fungicides available today, diseases caused by fungi still abound. Accordingly, there is ongoing research to create new and more effective fungicides for controlling or preventing diseases caused by phytopathic fungi.
It is therefore an object of the present invention to provide compounds which are highly effective for controlling or preventing phytopathogenic fungal infestations in agronomic crops, both growing and harvested.
It is also an object of the present invention to provide a method for the prevention, control or amelioration of a disease caused by a phytopathogenic fungus by contacting said fungus with a fungicidally effective amount of a compound.
These and other objects of the present invention will become more apparent from the detailed description thereof set forth below.